add async_exec_ifconfig_nic_down_up in test_stub
add async_exec_ifconfig_nic_down_up in test_stub

zstackorg/zstack-woodpecker,zstackio/zstack-woodpecker,zstackorg/zstack-woodpecker,zstackio/zstack-woodpecker,zstackio/zstack-woodpecker,zstackorg/zstack-woodpecker